Anthony Guglielmi, spokesman for the city's police department, said the Royal Canadian Mounted Police alerted the department Wednesday to the Twitter post, which he described as "a threat indicating an individual was threatening to do harm" at Forest Park High School.

Police searched the home, in the Gilmore Homes housing project, of the 15-year-old who was identified through his Twitter account — and who was not charged with a crime.

The search yielded no weapons, Guglielmi said, and the threat was deemed unfounded. Police did, however, find "green plant material in various forms of packaging," he said.

He said the boy was interviewed by prosecutors and detectives, and his case referred to juvenile court for counseling and monitoring.

Guglielmi said the notification from police counterparts in Canada reflected a heightened vigilance and partnership among law enforcement officials in the wake of a string of violent school incidents, particularly the massacre of 20 children and six educators at a Newton, Conn., elementary school last month.

"What people need to know is that there are a lot of eyes watching," he said. "Given the state of awareness we're all in, people can now have assurance that law enforcement from around the world are trying to protect us from these tragedies."

Prosecutors announced new indictments Monday of Baltimore jail staff, the same day a top corrections official testified in the federal corruption trial of eight inmates and corrections officers about the difficulty containing misconduct in the system.